A low weight/power/cost infrared Earth sensor

This paper describes and analyzes a <2.5 cu. in Earth sensor weighing <100 grams, providing /spl plusmn/1/spl deg/ single axis attitude readout accuracy for Earth orbit altitudes below 800 km. Above 800 km, orbit altitudes, the same volume sensor, can provide two axis attitude readout with the same or better accuracy. These low volumes, weights and costs are achieved by using the spacecraft computer to implement a proprietary algorithm that compensates for seasonal Earth horizon infrared radiance variations. This algorithm is described in this paper. Improvements in the /spl plusmn/1/spl deg/ accuracy can also be achieved by sensor fusion with a 40 gram two axis Sun sensor, which is described in a referenced paper.